Supplements containing extracts of the roots of Astragalus membranaceus are, according to the supplements industry, interesting for people who want to increase their resistance to infections. Researchers at the Hong Kong University of Science and Technology believe that the same supplements may also be worthwhile for endurance athletes. In test-tube studies Astragalus membranaceus boosts EPO synthesis.

According to classical Chinese medicine Astragalus membranaceus, or Huangqi as astragalus is called in Chinese, boosts Qi - our 'vital life force'. Danggui Buxue Tang, a herbal medicine that 'feeds the blood' contains an extract of roots of Astragalus membranaceus together with an extract of the roots of Angelica sinensis in a 5:1 ratio. A few years ago the researchers showed that Danggui Buxue Tang boosts the production of EPO in cells. In this study, published in 2011, they only looked at Astragalus membranaceus.

The roots of astragalus contain the flavonoids formononetin [1 in the figure below], ononin [2], calycosin [3] and calycosin-7-O-beta-D-glucoside [4]. Ononin is a sugared version of formononetin. Ononin and formononetin are also found in soya, but calycosin and calycosin-7-O-beta-D-glucoside are components typically found in Astragalus membranaceus.

Astragalus membranaceus also contains steroid compounds that the researchers refer to as astragalosides [5]. These play no role in this particular study. The researchers discovered that they did not boost the production of EPO.

When the researchers added their Astragalus membranaceus extract to kidney cells the latter started to produce more EPO. When the researchers repeated the experiment with the astragaloside flavonoids, it emerged that all four boosted the synthesis of EPO. The best EPO-booster was calycosin-7-O-beta-D-glucoside.

The researchers discovered that the Astragalus membranaceus flavonoids in the kidney cells activated the gene for HIF-1alpha. This gene is usually activated when cells are not getting enough oxygen, for example during extended periods of physical exertion or when time is spent in an oxygen deprived environment. The astragalus flavonoids lost their effect when the researchers exposed the kidney cells to HIF-1alpha inhibitors.

The researchers were not funded by supplements manufacturers but by the Croucher Foundation [croucher.org.hk] and the Research Grants Council of Hong Kong.